The text search engine allows queries to be formed from arbitrary Boolean expressions containing the keywords AND, OR, and NOT.
information retrieval
finds documents containing 'information' and 'retrieval'
information and retrieval
same as above
information or retrieval
finds documents containing either 'information' or 'retrieval'
information not retrieval
finds documents containing 'information' but not 'retrieval'
information near retrieval
finds documents where the two words a close to each other. The rank increases as word distance decreases.